4-19 



Thalassiosira/Cyclotella species represent a suite of species 

 including T. pseudonana (= Cyclotella nana) , T. rotula and T. norden- 

 skioldii . T. nordenskioldii , an important component of the Long Island 

 Sound phytoplankton community, was considered by Conover (1956) to 

 exhibit best growth during late-winter conditions of low light and 

 temperature. In New Haven Harbor, T. nordenskioldii was dominant in May 

 1975, and may have also been the major component of the Thalassiosira 

 sp. bloom from January through June and October through December of that 

 year (Table 4-2; Figure 4-6) . T. nordenskioldii was again dominant from 

 November 1976 through March 1977. Thus, along with S. costatum, T. 

 nordenskioldii probably contributed to the major late-winter phyto- 

 plankton blooms 1975 through 1977. 



Within the Thalassiosira/Cyclotella suite, Thalassiosira 

 pseudonana was the dominant taxon differentiated to species (Table 4-1) . 

 It reportedly experiences good growth at salinities from 4 /oo to 30 

 /oo (Guillard and Ryther, 1962) , and large blooms (>5 x 10 cells/1) 

 have been recorded in Great South and Moriches Bay, Long Island (Hul- 

 burt, 1970) . In New Haven Harbor, abundance peaks (10 -10 cells/1) 



occurred in May, June and/or July from 1974 through 1976 (Figure 4-7) . 



7 

 In 1977, however, peaks in April and August approached 10 cells per 



liter and appeared to be highest in the inner harbor. T. pseudonana 



probably contributed to the Cyclotella spp. and Thalassiosira spp. peaks 



observed from 1974 through 1977 (Figure 4-6, 4-7). 



Thalassionema nitzschioides is a cosmopolitan, principally- 

 neritic pennate diatom (Smayda, 1958) which experiences best growth at 

 low light and temperature levels but possesses wider tolerances in 

 southern stocks (Riley and Conover, 1967) . In New Haven Harbor, T. 

 nitzschioides has been consistently dominant from December through 

 February; during 1976 it was a dominant during all months except July 



through October and in 1977 it was dominant in February, March, June and 

 August (Table 4-2) . Highest densities (greater than 10 cells/liter) 

 occurred during March and May 1976 and in June 1977 (Figure 4-8) . 



(Text continued on page 4-23) 



